LONDON  British Prime Minister Tony Blair is trying to involve the United States in an new international treaty on global warming, The Times newspaper said on Thursday.

It said Blair had held lengthy discussions with U.S. President George W Bush over a fresh initiative that would bypass Washington's opposition to the Kyoto Protocol, which seeks to curb climate change.

The United States has not signed up to the Kyoto pact, which will go into effect in February after Russia ratified it in November.

"It is being given the highest priority," a Downing Street source was quoted as saying. "There is an awful lot of work going on in the background on this."

A Downing Street spokesman was unable to confirm the story, but said Blair had held talks with U.S. senator John McCain on the issue of climate change last week.